Base station apparatus and transmission method

Abstract

The present disclosure provides a method of generating codebook in a wireless communication system with multiple antenna arrays, as well as a wireless communication system, base station and terminal using the codebook for communication. The method comprises steps of: providing a basic codebook which contains multiple pre-coding matrices; and assigning phase offsets to certain pre-coding matrices in the basic codebook to form a codebook with phase offset. The feedback overhead from a client to a base station side is reduced and a good precision of feedback for multi-antenna array is kept by applying the method of generating codebook and using the generated codebook in the wireless communication system, base station and terminal.

The invention claimed is: 
     
       1. An integrated circuit, comprising:
 control circuitry which, in operation, controls:
 storing an extended codebook which is generated by combining a first basic codebook and a second basic codebook along a column direction, wherein the first basic codebook includes N groups, each consisting of four basic pre-coding column vectors (N is a natural number equal to or larger than 2), and wherein the second basic codebook is generated by applying phase offsets to the N groups, respectively, each of the phase offsets, applied to the N groups, being different from each other; 
 receiving, from a terminal apparatus via a multi-antenna array, information including a pre-coding matrix indicator (PMI) that identifies one pre-coding extended column vector from among 4N pre-coding extended column vectors included in the extended codebook; 
 pre-coding data using the pre-coding extended column vector identified by the PMI; and 
 
 at least one output, coupled to the control circuitry, which, in operation, outputs the pre-coded data for transmission via the multi-antenna array to the terminal apparatus. 
 
     
     
       2. The integrated circuit according to  claim 1 , wherein:
 each of the first basic codebook and the second basic codebook includes 4N basic pre-coding column vectors, each having four rows and one column; and 
 the extended codebook includes the 4N pre-coding extended column vectors, each having eight rows and one column. 
 
     
     
       3. The integrated circuit according to  claim 1 , wherein:
 the four basic pre-coding column vectors are orthogonal to each other in each of the N groups. 
 
     
     
       4. The integrated circuit according to  claim 1 , wherein:
 an angle difference between a basic pre-coding matrix w m  and a basic pre-coding matrix w m+1  included in the first basic codebook is an integer multiple of 2π/32, wherein m is an integer. 
 
     
     
       5. The integrated circuit according to  claim 1 , wherein:
 the at least one output, in operation, outputs the pre-coded data for transmission from a base station apparatus using two layers, 
 the basic pre-coding column vectors included in the first basic codebook respectively include basic pre-coding matrix vectors w m  for one of the two layers and basic pre-coding matrix vectors w′ m  for another one of the two layers, where m is an integer; and 
 an angle difference between the vectors w m  and w′ m  is selected from a set of angles including: 2π/32, 4π/32 and 6π/32. 
 
     
     
       6. The integrated circuit according to  claim 1 , wherein:
 the integrated circuit is part of a base station apparatus that includes a plurality of array antennas; and 
 the PMI is for each of the plurality of array antennas.